This invention relates to hydrogen peroxide destroying compositions, and the use of same, to decrease the concentration of, or even substantially eliminate, hydrogen peroxide present in a liquid medium. More particularly, the invention relates to such compositions which are useful in destroying residual hydrogen peroxide present in a liquid aqueous medium containing a contact lens which has been disinfected by the action of hydrogen peroxide.
Contact lenses should be periodically cleaned and disinfected by the user to prevent infection or other deleterious effects on ocular health which may be associated with contact lens wear. Currently, there are several different conventional systems and methods which enable the user to clean and disinfect their .contact lenses between wearing times. These conventional cleaning and disinfection systems can be divided into "hot" and "cold" systems. Hot systems require the use of heat to disinfect the contact lenses, whereas cold systems use chemical disinfectants at ambient temperatures to disinfect the lenses.
Within the realm of cold disinfection systems are hydrogen peroxide disinfection systems. Disinfecting hydrogen peroxide solutions are effective to kill the bacteria and fungi which may contaminate contact lenses. However, residual hydrogen peroxide on a disinfected contact lens may cause irritation, burning or trauma to the eye unless this hydrogen peroxide is destroyed, i.e., decomposed, neutralized, inactivated or chemically reduced. Therefore, the destruction of the residual hydrogen peroxide in the liquid medium containing the disinfected contact lens is needed to enable safe and comfortable wear of the disinfected contact lens.
Associated with the problem of hydrogen peroxide destruction in contact lens disinfection systems are the problems of easy use and user compliance. To enhance user compliance and ease of use, several efforts have focused on one-step disinfection and hydrogen peroxide destruction. In this regard, various time release tablets containing a core tablet and a totally soluble or insoluble coating have been suggested.
Kruse et al U.S. Pat. No. 4,767,559 discloses a one-step contact lens cleaning and disinfecting tablet designed to be totally dissolved in water. A core containing a hydrogen peroxide reducing agent and a catalyst is provided. Preferably but not essentially, a thin lacquer polymeric coating, e.g., of acrylic resin or polyvinylpyrrolidone, may be sprayed on the core tablet to form an enveloped core tablet. A non-polymeric jacket mixture containing a hydrogen peroxide generating component is dry coated into the enveloped core tablet. In this case, the jacket mixture dissolves to form hydrogen peroxide to disinfect the contact lens. Subsequently, the thin lacquer polymeric coating enveloping the core tablet is dissolved, resulting in the release of the reducing agent and catalyst. Spraying the thin lacquer polymeric coating on as a liquid mixture, e.g., aqueous solution, can be disadvantageous. For example, the liquid in the mixture may require additional time to evaporate or may not entirely evaporate. This prolongs the tablet production process. In addition, if polyvinylpyrrolidone-containing liquid is sprayed on the core tablet to form the thin lacquer polymeric coating, the coated tablets tend to stick together, thus making further processing more difficult. Further, using a liquid mixture can result in an uneven, or even discontinuous, coating of the core tablet. Also, using liquid solutions of certain polymers is not effective to provide a coating of sufficient thickness to act as a practical delayed release coating.
Schafer et al European Patent Application 86-109,361.5 discloses a hydrogen peroxide neutralizer tablet covered with a water-soluble coating to delay the dissolution of the tablet. The coating is applied by conventional procedures such as by spraying on a film in coating pans, by fluidized bed methods, or in closed systems. This publication does not suggest that the delayed release coating be applied as anything but a liquid. Also, polyvinylpyrrolidone is described as a component of the neutralizer tablet, but not as a component of the coating.
There continues to be a need for a one step contact lens disinfecting system using a hydrogen peroxide destroying component. Tablets which include such components should not stick together during manufacture or storage. Also, the delayed release coating should be of sufficient thickness to allow enough time for lens disinfecting to take place while, at the same time allowing release of the hydrogen peroxide destroying component in a reasonable period of time so that the disinfected lens can be safely and comfortably worn.